When using a low air permeability resin as an air permeation preventive layer, laminating the same with rubber, and vulcanizing the laminate, the air contained in the rubber and the gas produced due to the vulcanization reaction cause the increase in the pressure of the gas in the rubber. At this time, if the laminated low permeability resin is low in Young's modulus (i.e., strength), when the pressure is released after vulcanization, a negative pressure is applied to the layer, and therefore blistering occurs and a sufficient gas barrier property cannot be imparted. In particular, this tendency becomes remarkable in a laminate of an air permeation preventive layer composed of a low air permeability resin sandwiched between the rubbers. An ethylene vinyl alcohol copolymer (EVOH) has a superior gas barrier property, and, therefore, can give an air pressure retention performance of at least that of a conventional butyl liner, with a thickness of several μm, but has a low heat resistance (or melting point) of 150 to 195° C. There is the problem that, depending on the vulcanization conditions, the EVOH will be exposed to a temperature near or higher than the melting point to thereby result in the possible destruction of the layer (i.e., blistering).
Japanese Patent Publication (A) No. 2002-79804 discloses the (electron beam) cross-linkable polyvinyl alcohol EVOH. This cross-links the EVOH as a measure against wear of the EVOH and teaches improvement in the heat resistance.